None of this is hot air, that’s the problem. Yes, of course there will be all sorts of opinions on why there should be a ceasefire represented amongst those marching, including the opinions of those who support Hamas and do not want Israel to exist at all and those who are deeply antisemitic in general. Yes, of course the longer this goes on, the more the antisemites and terrorist sympathisers will try to inveigle their opinions into the mainstream, and I can’t see it being anything other than terrifying for Jewish families and alarming for everyone else. This is also a grand opportunity for Islamophobes and racists to push their opinions into the mainstream at every opportunity.
The problem is, marches are aimed at exerting political pressure on the government of the country where the marches are taking place. A march just asking for “peace” is, tbh, a bit pointless from a political viewpoint, as already recognised by @floodlightonwhatisright , because the marchers have no political influence whatsoever over Israel or Hamas, and the UK government is hardly going to say it doesn’t support peace. What the UK government has made clear, however, is that it already condemns Hamas’ actions in October and already views it as nothing more than a terrorist group, so there is no change to be pushed for there. Where the UK government is falling short, in the view of a great many people and 100% of the people marching, is in its failure to condemn Israel’s ongoing response. The marches are aimed at putting pressure on this Government to change its response to Israel’s reaction, not on directly convincing Israel or Hamas that they should “give peace a chance.” As a consequence, the marches will no doubt continue until the UK government becomes more even handed in its condemnation of the mutual atrocities committed.